Hameenlinna have caused the second major upset of the playoffs already, after 11th seeds Pelicans completed a 3-0 series whitewash over JYP 24 hours earlier, and have done it after recovering from a loss in the first match.
The unlikely winning streak for the side who lost three of the last four in the regular season looked to be continuing in the 13th minute when Cameron Wright stole the puck in Lukko territory and beat the goaltender at his near post for his third goal of the series.
Things got worse for the visitors early in the second period when Ponthus Westerholm was called for hooking, and on the powerplay, Wright had time and space on the right to send the puck in front of the net, where Sami Paivarinta was on hand to divert it in.
It was 3-0 five minutes before the end of the second, as Thomas Caron's powerful finish flew into the net, and though Jakob Stenqvist pulled one back for Lukko with six minutes to go, comeback hopes were ended just two minutes later through Anrei Hakulinen's empty-net goal to make it 4-1.
Hameenlinna will face top seeds Tappara in the quarter-finals, while Pelicans are now confirmed to meet KooKoo in the best-of-seven series.
After two overtime losses put them on the brink of suffering a sweep, Kiekko-Espoo have levelled their series with Assat at 2-2 following a 4-1 victory on home ice.
The visitors knew a win would take them to the quarter-finals with a game to spare, and began well, as Jonne Tammela put them ahead as early as the second minute.
That's how things stayed until the midpoint of the game when the KE turnaround began - Cameron Hillis drew his side level on a powerplay after Arttu Alasiurua was called for slashing, and just over five minutes later Santeri Virtanen reacted quickest to a loose puck and fired the hosts ahead.
Midway through the third period, the Espoo side again turned to Hillis, whose second of the game gave Kiekko a two-goal cushion, which they extended in the final three minutes, when Jere Vaisanen struck the puck into the Aces' empty net.
KalPa have also kept their season alive and levelled their series with IFK Helsinki thanks to a crucial 4-1 win on the road, the third 4-1 scoreline of the series and the third in three games this evening.
After neither side found the net in 60 minutes in game three, the goals were again hard to come by -Konsta Kapanen broke the deadlock for the reigning champions in the ninth minute, but it took until the final three minutes of period two for Joona Saarelainen to add some breathing space.
Aleksi Klemetti added a third, five minutes into the third period, and though Petr Kodytek finally got HIFK on the board inside the final nine minutes, it was already looking like too little too late for the home side before Andreas Okany slotted into the empty net to wrap up the win.
KalPa will host HIFK and Assat welcome Kiekko-Espoo for their deciding matches on Thursday 26th March.